This invention relates to combining chemical reaction with product separation, that is, catalytic distillation. Continuous removal of reaction products is a unique feature that gives catalytic distillation its technical and economic advantages. Advantages include lower energy requirements, higher yields, good product purity, and lower capital investment.
In catalytic distillation, a reaction zone, containing catalysts, is fitted into a fractionation tower conventionally equipped with an overhead condenser, reflux pump, reboiler, and control instrumentation. Depending upon boiling points, feed components are introduced above or below the catalyst bed. Products are continuously removed from the reaction zone by the distillation process.
Catalytic distillation is suitable only for chemical reactions where the distillation of reaction components occurs in the same temperature range as the reaction. Thus, operation above the critical point can be a limitation, and the presence of azeotropes or close boiling components may cause difficulties.
The catalyst must be stable and insoluble in the feed or product. It should be relatively immune to poisoning because frequent replacement can be costly. The selective catalyst, which must be a solid material, can be contained in pockets stitched into fiberglass cloth. The cloth is rolled into bundles with alternate layers of wire mesh. In operation, liquid flows freely into and out of the bundles, providing a constant exchange over the catalyst surface.
Multiple bundles of various diameters are used to cover the cross section of the distillation column and each layer of bundles is staggered to prevent by-passing. The total bed height, or reaction zone, and its position in the column are determined by the feed type and composition, and the products and purity desired.
The reaction occurs in the liquid phase in the presence of a solid catalyst.
Catalytic distillation has been used commercially to produce methyl tert-butyl ether. See W. Stadig, Catalytic Distillation, Chemical Processing (February, 1987). See U.S. Pat. Nos. 4,232,177 and 4,307,254.
Catalytic distillation has also been used to produce cumene by alkylating propylene with benzene. See J. Shoemaker et al, Cumening By Catalytic Distillation, Hydrocarbon Processing, p. 57 (June, 1987).
U.S. Pat. Nos. 4,242,530 and 4,215,011 relate to a catalytic distillation technique for the separation of isobutene from a mixture comprising n-butene and isobutene. Catalyst suitable for the process are taught to be cation exchangers, which contain sulfonic acid groups, and which has been obtained by polymerization or copolymerization of aromatic vinyl compounds followed by sulfonation.
U.S. Pat. No. 4,510,336 relates to transetherification carried out in a catalytic distillation reactor. There, an ether is fed to a catalyst bed to partially dissociate it into a first olefin and a first alcohol while concurrently feeding a second olefin or a second alcohol having a higher boiling point to form a second ether. Catalyst suitable for the distillation are cation exchangers which contain sulphonic acid groups.
European Patent Application No. 189,683 relates to aromatic compounds that are alkylated in a catalytic distillation. The catalyst can be a suitable cation exchange resin including those containing sulphonic acid groups. The catalyst can also be a molecular sieve, which includes both naturally occurring zeolites and synthetic zeolites.
U.S. Pat. No. 4,384,161 relates to a heterogeneous isoparaffin/olefin alkylation. This process comprises contacting the isoparaffins and olefins with a composite catalyst comprising a large pore zeolite and a Lewis acid. Similary, U.S. Pat. Nos. 3,855,342 and 3,862,258 relate to such alkylations but using a complex of a macroreticular acid cation exchange resin and BF.sub.3 with or without the addition of water. None of these processes relate to catalytic distillation.
The preceding references are incorporated by reference.
The present invention relates to alkylation and oligomerization processes utilizing a catalyst comprising a Lewis acid promoted non-zeolitic solid inorganic oxide, large pore crystalline molecular sieve and/or ion exchange resin, which can be in the presence of water, which is effected by catalytic distillation techniques.